1. Field of the Invention
The present invention relates to the prevention and removal of stains on the surfaces of swimming pools and spas, particularly cobalt stains on fiberglass pools and spas.
2. Description of the Prior Art
For many years most public and private swimming pools were constructed of poured concrete covered with plaster on the concave surfaces containing the swimming water. More recently, swimming pools had been constructed of fiberglass. Unlike concrete pools, fiberglass pools can be preformed in factories and transported to the location at which the swimming pool is to be installed. Fiberglass swimming pools are far lighter in weight compared with plaster covered concrete pools. The ability to manufacture the structure of the pool from fiberglass and to thereafter transport the pool has markedly reduced the cost of swimming pool construction. Small fiberglass pools can be constructed as unitary structures, while larger pools are typically constructed in sections which are transported to the location at which the pool is to be installed. At the location the fiberglass structures are juxtaposed and bonded together with fiberglass and resin.
Due in large part to the economy with which fiberglass pool structures can be manufactured, fiberglass pools are now installed in a far greater number of residences than was previously the case. Also, fiberglass spas have become quite a popular item in many residential structures. Fiberglass spas and tubs can be manufactured as unitary structures and transported to an installation site with relatively little difficulty. Such spas and hot tubs provide a welcome source of relaxation to many people.
Fiberglass pools, spas and tubs are manufactured from filamentary or chopped strands of glass bonded together by epoxy or polyester resins. The exposed surfaces of fiberglass pools, spas and tubs are typically coated with an overlying gel coat or acrylic layer to provide a hard, protective finish and to provide a smooth, glossy luster to the structure.
One persistent problem with fiberglass pools and spas has been the formation of cobalt stains on the fiberglass surfaces. The cobalt stains are dark splotches on the fiberglass surfaces. Although the splotches resemble and are often mistaken for algae or mildew, they are actually inorganic stains. The formation of such stains has been attributed to the reaction between metals and minerals which are present in tap water used to fill the pools and spas and the fiberglass, resins and gel coat or acrylic finishes on the surfaces of fiberglass pools. The stains which are formed are ink-like splotches. Most fiberglass pools and spas develop such stains and no satisfactory treatment to remove and prevent such stains has heretofore been developed.
Cobalt stains are known in the field of pool maintenance by various names. Among these names are cobalt stains, kobalt staining, brown plaque, black plaque, gel coat plaque, black spotting and black staining. All such terms refer to the same type of stain, and will hereinafter be referred to collectively as cobalt stains.
While cobalt stains are extremely common, and indeed appear in most fiberglass pools and spas, no effective technique of dealing with the problem has heretofore been utilized. Because cobalt stains resemble algae and mildew in appearance, they are often treated as organic in origin. Most aleae treatments employ metal based chemicals. Because cobalt stains result from a reaction of metals in water, the treatment of such stains with chemicals used to control algae merely aggravates the problem.
The only way in which cobalt stains have heretofore been removed has been by sanding. Sanding damages the surface finish of fiberglass pools and spas and harms the appearance. Moreover, sanding requires a considerable time and is therefore quite expensive.
Various chemicals have been devised to cover up cobalt stains. However, the stains are not removed and the surface cover-up detracts from the appearance of the spa or pool.